This proposed investigation is directed toward the delineation of gonadal steroids throughout the reproductive cycle of the nine-banded armadillo (Dasypus novemcinctus). These data will provide the first measurements of circulating gonadal steroids in this species and greatly enhance the present understanding of the reproductive processes in this unique and potentially useful animal model. Since a lack of breeding in captivity represents the major obstacle to the application of this species as a laboratory animal, the proposed study will provide critical information for the subsequent development of breeding colonies. Additional studies are designed to examine the role of gonadal steroids during the period of delayed implantation and nidation. Due to the unusual quality of polyembryony in the armadillo, the ability to modulate the time of implantation should provide new insight into the mechanisms of twinning as well as provide a unique model for application in perinatology. The development of methods for the induction of ovulation in this study and artificial insemination as proposed will allow complete versatility of this species in reproductive studies in captivity.